In the world of modular synthesis, Doepfer is an unarguable giant. Doepfer introduced the world to the Eurorack format in the late 1990s, offering a well-defined standard & infrastructure for a new generation of modular synthesizer. He unknowingly opened the floodgates for what would become an explosive industry. In many ways, the bulk of the current modular synthesizer scene's successes are built on the infrastructure that Doepfer developed: manufacturers like Make Noise and Industrial Music Elektronics (FKA The Harvestman) have both expressed that their earliest creations were intended as extensions of Doepfer's A-100 system, not realizing just how popular their own designs might become.

Even at the outset, the Doepfer product line was formidable: dozens of modules that allowed for a wide array of sound design opportunities from traditional subtractive synthesis to much more esoteric, peculiar fare. Enormous systems comprised of clean, starkly-labeled panels heralded back to the day of towering Moog and E-Mu systems and promised younger musicians the first easy, affordable access to the almost mystically alluring world of modular synthesis.

The A-110-6 not only sports positively killer exponential and linear thru-zero FM, but also offers a wide array of separate waveshape outputs: triangle, sine, rectangle, saw, and a novel, Synthi-like trapezoid waveshape are all accessible simultaneously—excellent for mixing together complex waveshapes in VCO or LFO modes. Furthermore, an extra output is included for each of these shapes (cosine, "tricosine," "reccosine", etc.), offering matched wave shapes 90 degrees out of phase with the primary outputs. This makes it possible for the A-110-6 to create circular panning when combined with a quadraphonic panner like the Antimatter V3KT or Intellijel Planar 2, as well as a host of other cascaded modulations.

Ten simultaneous distinct waveshape outputs, exponential FM, linear thru-zero FM, and seamless operation in audio and LFO ranges might make this the coolest Doepfer oscillator, if not one of the coolest analog oscillators available altogether.

The Doepfer A-137 seems to be a direct descendant of the concepts in the Buchla 259 and Serge VCM, with even more control than offered in either of these forerunners. Like many wavefolders, the A-137 provides controls for wavefold amount (labelled "multiples" here) and bias (often referred to as "symmetry"), but provides additional controls for input level, wavefolding threshold ("folding level"), and output waveshape smoothness ("harmonics," controlled by an additional VCA for each folding stage). All of these options result in what may be the most highly configurable Eurorack wavefolder module, and the sound itself is the proof: the A-137 does everything from subtle Music Easel-like coloration to Serge growls and completely unheard, harmonically rich modulations.

The A-137 provides a broad range of sounds and requires a bit of finesse to find just the right one: but once you get there, it has an unmistakably deep, rich sound. Another quick tip: try combining this module with a mixer or crossfader at its input to introduce feedback into the signal path. Smooth cascading modulations, grinding distortion, and terrifying howls will emerge with careful tuning.

Doepfer's A-149-1 is yet another A-100 module inspired by the Buchla legacy: this time, by the iconic 266 Source of Uncertainty. The Source of Uncertainty is famous for its semi-controllable nature, generating random voltages that are easy to wrangle in into more-or-less predictable ranges under manual or voltage control. It is comprised of two sections: Quantized Random Voltages and Stored Random Voltages.

The Quantized Random Voltage section provides stepped random voltages when presented with a gate at the clock input, in some ways not unlike the traditional noise–>S&H setup. Where it differs from this "classic random" patch is that it provides the user the option to constrain the number of choices of output voltage possible. By using the Manual N control and CV N input, the user can determine the behavior of the N+1 and 2^N outputs, with the N factor variable between 1 and 6. This means that the N+1 output at minimum setting will choose randomly between only two output voltages, and at maximum will choose randomly between only seven distinct output voltages; likewise, the 2^N output produces 2 distinct voltages at minimum, 64 distinct voltages at maximum. This opens a world of opportunities not conceivable in the typical S&H patch, where a theoretically infinite voltage resolution is possible—specific "random" pitches begin to make themselves apparent, specific rhythmic sets begin to emerge, and more: as it turns out, this type of randomness is, for lack of better words, musical. It is like a typical random source—but far more controllable.

A closer look at the A-149-1

The Stored Random Voltage section provides similar control over the predictability of its output, just through different means. Whereas the Quantized section offers control of the distinct number of output voltage options, the Stored section provides continuous control over probability Distribution: when the D control is set to maximum, output voltages will tend to be fairly high; when set to minimum, they tend to be fairly low. Manual and CV control over the D parameter makes it possible to create randomness that shifts gradually from low to high or vice versa, providing dynamic randomness difficult to achieve through other means.

Oh, and as a bonus, the Stored section also features a dedicated even distribution output: making it possible to use this module to produce four distinct, simultaneous stepped random voltages. Try pairing it with the A-149-2 Digital Random Voltages Expander to create eight random gates as well!